Preheat the oven to 375F.
Place the butter in a large mixing bowl or the bowl of a stand mixer and sift the flour, sugar, baking powder and salt over top. Blend slowly together over medium-low speed until mixture resembles pebbles.
Add in ½ cup of milk and the egg, mix on medium until the flour mixture is completely moistened and the egg has been incorporated.
Add the remaining milk and vanilla and mix until just combined--it's ok if there are some lumps in the batter.
Place the paper liners in your muffin tin and fill the cupcake liners about ¾ of the way full.
Bake in the centre of the oven for 18-20 minutes or until a toothpick inserted into the middle comes out clean. Remove from oven and allow to cool before frosting.